Vibration measurements based on demodulating the phase of a fiber 3dB-coupler Michelson interferometer

Min Li; Fang Xie; Junyu Ren

doi:10.1117/12.837952

20 November 2009 Vibration measurements based on demodulating the phase of a fiber 3dB-coupler Michelson interferometer

Min Li, Fang Xie, Junyu Ren

Proceedings Volume 7511, 2009 International Conference on Optical Instruments and Technology: Optoelectronic Measurement Technology and Systems; 75110C (2009) https://doi.org/10.1117/12.837952
Event: International Conference on Optical Instrumentation and Technology, 2009, Shanghai, China

Abstract

A fiber interferometric vibration measurement system which is based on demodulating the phase of a fiber Michelson interferometer which is made with a fiber 3dB-coupler is presented. In the work, the system employed the characteristics of fiber Brag gratings (FBGs) to interleave two fiber Michelson interferometers which share almost the same part of the main optical path. One of the fiber interferometers is used to stabilize the system, employing an electronic feedback loop to drive a piezoelectric actuator to tune the optical path of the reference beam in order to keep the interferometer in quadrature state. By this way, the low frequency drifts in the phase of the interferometric signals which are resulted from environmental disturbances are compensated for. The other one is used to perform the measurement task. By employing the characteristics of 3dB-coupler, the interferometric signals from the two outputs of the 3dB-couper are 180º out of phase. The two interferometric signals are input into an electronic processor and convert into currents, which are linear to the power of the optical interferometric light. The signals are collected by NI USB-5132 acquisition card and processed by a program in a personal computer. The measurement system is configured with fiber and fiber components which are integrated together. As the cutoff frequency of the feedback loop is 1.5Hz, the measurement system is capable of measuring vibration with frequencies bigger than 1.5Hz and the amplitude of the measured vibration is not limited.

Citation Download Citation

Min Li, Fang Xie, and Junyu Ren "Vibration measurements based on demodulating the phase of a fiber 3dB-coupler Michelson interferometer", Proc. SPIE 7511, 2009 International Conference on Optical Instruments and Technology: Optoelectronic Measurement Technology and Systems, 75110C (20 November 2009); https://doi.org/10.1117/12.837952

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KEYWORDS

Interferometry

Interferometers

Michelson interferometers

Signal detection

Signal processing

Mirrors

Feedback loops

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